FIG. 1 shows a cross-sectional view of a read-write head of the prior art. Seen there are substrate 10 on which is undercoat 11. Magnetic read unit 13 is seen sandwiched between reader shields 12. The read unit is a magneto-resistive type such as a GMR (giant magneto-resistance) or MTJ (magnetic tunnel junction).
Directly above the upper of the two shields 12 is horizontal portion 14 of the bottom pole from which vertical portion 15 extends, its outer edge being part of the ABS (air bearing surface). Some distance away from vertical bottom pole 15 is yoke 16 that also extends upwards from the horizontal bottom pole, but to a slightly greater height than the vertical lower pole. Non-magnetic write gap layer 20 lies on vertical pole 15 and extends from the ABS to the edge of yoke 16.
Surrounding yoke 16 is coil(s) 17, the number of coils being a design choice which will be discussed in greater detail below. Hard-baked photoresist 18 is used to encapsulate the coil(s) as well as the yoke. The writer magnetic circuit is completed through top pole 21 which is in magnetic contact with yoke 16 and is separated from vertical pole 15 by write gap layer 20. The structure of FIG. 1 is completed by filler insulation 19 and by overcoat layer 22.
As areal density requirements have become more stringent for magnetic recording read/write heads, the complexity of the writer structure design has grown significantly. The need for a higher number of coil turns in the writer for stronger overwrite magnetic field, while minimizing the coil DC resistance, result in a trend to multi-layer coil writer structures. The frequency extendability requirement for higher data rate applications dictates the need for a shorter yoke length and the associated lower inductance, which also necessitates a multi-coil layer writer structure. While this achieves the required magnetic performance, the multi-layer coil writer has an intrinsic deficiency—poor heat dissipation for the upper (top) layer coils. Higher thermal pole tip protrusion during writer activation resulting from this drawback creates reliability problems relative to single-layer coil writer designs.
A routine search of the prior art was performed with the following references of interest being found:
In U.S. Pat. No. 6,181,514, Santini et al. disclose a non-organic insulating material on the coil as a heat dissipater. In U.S. Pat. No. 6,466,404, Crue, Jr. et al. show AlN or other material as an undercoat under the coil to dissipate heat and, in U.S. Pat. No. 6,381,094, Gill teaches using gold and tantalum as a heat sink layer.